src/game/java/com/mojang/blaze3d/vertex/BufferBuilder.java

package com.mojang.blaze3d.vertex;

import java.nio.ByteOrder;
import java.util.stream.Collectors;
import javax.annotation.Nullable;
import net.minecraft.util.ARGB;
import net.minecraft.util.Mth;
import net.minecraftforge.api.distmarker.Dist;
import net.minecraftforge.api.distmarker.OnlyIn;
import org.lwjgl.system.MemoryUtil;

@OnlyIn(Dist.CLIENT)
public class BufferBuilder implements VertexConsumer {
    private static final long NOT_BUILDING = -1L;
    private static final long UNKNOWN_ELEMENT = -1L;
    private static final boolean IS_LITTLE_ENDIAN = ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN;
    private final ByteBufferBuilder buffer;
    private long vertexPointer = -1L;
    private int vertices;
    private final VertexFormat format;
    private final VertexFormat.Mode mode;
    private final boolean fastFormat;
    private final boolean fullFormat;
    private final int vertexSize;
    private final int initialElementsToFill;
    private final int[] offsetsByElement;
    private int elementsToFill;
    private boolean building = true;

    public BufferBuilder(ByteBufferBuilder p_342927_, VertexFormat.Mode p_344709_, VertexFormat p_342329_) {
        if (!p_342329_.contains(VertexFormatElement.POSITION)) {
            throw new IllegalArgumentException("Cannot build mesh with no position element");
        } else {
            this.buffer = p_342927_;
            this.mode = p_344709_;
            this.format = p_342329_;
            this.vertexSize = p_342329_.getVertexSize();
            this.initialElementsToFill = p_342329_.getElementsMask() & ~VertexFormatElement.POSITION.mask();
            this.offsetsByElement = p_342329_.getOffsetsByElement();
            boolean flag = p_342329_ == DefaultVertexFormat.NEW_ENTITY;
            boolean flag1 = p_342329_ == DefaultVertexFormat.BLOCK;
            this.fastFormat = flag || flag1;
            this.fullFormat = flag;
        }
    }

    @Nullable
    public MeshData build() {
        this.ensureBuilding();
        this.endLastVertex();
        MeshData meshdata = this.storeMesh();
        this.building = false;
        this.vertexPointer = -1L;
        return meshdata;
    }

    public MeshData buildOrThrow() {
        MeshData meshdata = this.build();
        if (meshdata == null) {
            throw new IllegalStateException("BufferBuilder was empty");
        } else {
            return meshdata;
        }
    }

    private void ensureBuilding() {
        if (!this.building) {
            throw new IllegalStateException("Not building!");
        }
    }

    @Nullable
    private MeshData storeMesh() {
        if (this.vertices == 0) {
            return null;
        } else {
            ByteBufferBuilder.Result bytebufferbuilder$result = this.buffer.build();
            if (bytebufferbuilder$result == null) {
                return null;
            } else {
                int i = this.mode.indexCount(this.vertices);
                VertexFormat.IndexType vertexformat$indextype = VertexFormat.IndexType.least(this.vertices);
                return new MeshData(bytebufferbuilder$result, new MeshData.DrawState(this.format, this.vertices, i, this.mode, vertexformat$indextype));
            }
        }
    }

    private long beginVertex() {
        this.ensureBuilding();
        this.endLastVertex();
        this.vertices++;
        long i = this.buffer.reserve(this.vertexSize);
        this.vertexPointer = i;
        return i;
    }

    private long beginElement(VertexFormatElement p_343872_) {
        int i = this.elementsToFill;
        int j = i & ~p_343872_.mask();
        if (j == i) {
            return -1L;
        } else {
            this.elementsToFill = j;
            long k = this.vertexPointer;
            if (k == -1L) {
                throw new IllegalArgumentException("Not currently building vertex");
            } else {
                return k + (long)this.offsetsByElement[p_343872_.id()];
            }
        }
    }

    private void endLastVertex() {
        if (this.vertices != 0) {
            if (this.elementsToFill != 0) {
                String s = VertexFormatElement.elementsFromMask(this.elementsToFill).map(this.format::getElementName).collect(Collectors.joining(", "));
                throw new IllegalStateException("Missing elements in vertex: " + s);
            } else {
                if (this.mode == VertexFormat.Mode.LINES || this.mode == VertexFormat.Mode.LINE_STRIP) {
                    long i = this.buffer.reserve(this.vertexSize);
                    MemoryUtil.memCopy(i - (long)this.vertexSize, i, (long)this.vertexSize);
                    this.vertices++;
                }
            }
        }
    }

    private static void putRgba(long p_344481_, int p_342528_) {
        int i = ARGB.toABGR(p_342528_);
        MemoryUtil.memPutInt(p_344481_, IS_LITTLE_ENDIAN ? i : Integer.reverseBytes(i));
    }

    private static void putPackedUv(long p_344069_, int p_342894_) {
        if (IS_LITTLE_ENDIAN) {
            MemoryUtil.memPutInt(p_344069_, p_342894_);
        } else {
            MemoryUtil.memPutShort(p_344069_, (short)(p_342894_ & 65535));
            MemoryUtil.memPutShort(p_344069_ + 2L, (short)(p_342894_ >> 16 & 65535));
        }
    }

    @Override
    public VertexConsumer addVertex(float p_342038_, float p_342902_, float p_344845_) {
        long i = this.beginVertex() + (long)this.offsetsByElement[VertexFormatElement.POSITION.id()];
        this.elementsToFill = this.initialElementsToFill;
        MemoryUtil.memPutFloat(i, p_342038_);
        MemoryUtil.memPutFloat(i + 4L, p_342902_);
        MemoryUtil.memPutFloat(i + 8L, p_344845_);
        return this;
    }

    @Override
    public VertexConsumer setColor(int p_345246_, int p_343163_, int p_342676_, int p_345202_) {
        long i = this.beginElement(VertexFormatElement.COLOR);
        if (i != -1L) {
            MemoryUtil.memPutByte(i, (byte)p_345246_);
            MemoryUtil.memPutByte(i + 1L, (byte)p_343163_);
            MemoryUtil.memPutByte(i + 2L, (byte)p_342676_);
            MemoryUtil.memPutByte(i + 3L, (byte)p_345202_);
        }

        return this;
    }

    @Override
    public VertexConsumer setColor(int p_342265_) {
        long i = this.beginElement(VertexFormatElement.COLOR);
        if (i != -1L) {
            putRgba(i, p_342265_);
        }

        return this;
    }

    @Override
    public VertexConsumer setUv(float p_344538_, float p_343862_) {
        long i = this.beginElement(VertexFormatElement.UV0);
        if (i != -1L) {
            MemoryUtil.memPutFloat(i, p_344538_);
            MemoryUtil.memPutFloat(i + 4L, p_343862_);
        }

        return this;
    }

    @Override
    public VertexConsumer setUv1(int p_345138_, int p_344474_) {
        return this.uvShort((short)p_345138_, (short)p_344474_, VertexFormatElement.UV1);
    }

    @Override
    public VertexConsumer setOverlay(int p_343250_) {
        long i = this.beginElement(VertexFormatElement.UV1);
        if (i != -1L) {
            putPackedUv(i, p_343250_);
        }

        return this;
    }

    @Override
    public VertexConsumer setUv2(int p_343260_, int p_345129_) {
        return this.uvShort((short)p_343260_, (short)p_345129_, VertexFormatElement.UV2);
    }

    @Override
    public VertexConsumer setLight(int p_342358_) {
        long i = this.beginElement(VertexFormatElement.UV2);
        if (i != -1L) {
            putPackedUv(i, p_342358_);
        }

        return this;
    }

    private VertexConsumer uvShort(short p_342039_, short p_345222_, VertexFormatElement p_344482_) {
        long i = this.beginElement(p_344482_);
        if (i != -1L) {
            MemoryUtil.memPutShort(i, p_342039_);
            MemoryUtil.memPutShort(i + 2L, p_345222_);
        }

        return this;
    }

    @Override
    public VertexConsumer setNormal(float p_342317_, float p_342276_, float p_342607_) {
        long i = this.beginElement(VertexFormatElement.NORMAL);
        if (i != -1L) {
            MemoryUtil.memPutByte(i, normalIntValue(p_342317_));
            MemoryUtil.memPutByte(i + 1L, normalIntValue(p_342276_));
            MemoryUtil.memPutByte(i + 2L, normalIntValue(p_342607_));
        }

        return this;
    }

    private static byte normalIntValue(float p_344123_) {
        return (byte)((int)(Mth.clamp(p_344123_, -1.0F, 1.0F) * 127.0F) & 0xFF);
    }

    @Override
    public void addVertex(
        float p_343280_,
        float p_344969_,
        float p_343237_,
        int p_342708_,
        float p_345023_,
        float p_344850_,
        int p_344316_,
        int p_342457_,
        float p_344002_,
        float p_344052_,
        float p_343783_
    ) {
        if (this.fastFormat) {
            long i = this.beginVertex();
            MemoryUtil.memPutFloat(i + 0L, p_343280_);
            MemoryUtil.memPutFloat(i + 4L, p_344969_);
            MemoryUtil.memPutFloat(i + 8L, p_343237_);
            putRgba(i + 12L, p_342708_);
            MemoryUtil.memPutFloat(i + 16L, p_345023_);
            MemoryUtil.memPutFloat(i + 20L, p_344850_);
            long j;
            if (this.fullFormat) {
                putPackedUv(i + 24L, p_344316_);
                j = i + 28L;
            } else {
                j = i + 24L;
            }

            putPackedUv(j + 0L, p_342457_);
            MemoryUtil.memPutByte(j + 4L, normalIntValue(p_344002_));
            MemoryUtil.memPutByte(j + 5L, normalIntValue(p_344052_));
            MemoryUtil.memPutByte(j + 6L, normalIntValue(p_343783_));
        } else {
            VertexConsumer.super.addVertex(
                p_343280_, p_344969_, p_343237_, p_342708_, p_345023_, p_344850_, p_344316_, p_342457_, p_344002_, p_344052_, p_343783_
            );
        }
    }
}